Using breakable hyphen "= in \newcommand

Question

I want to use a breakable hyphen "= in a command:

\documentclass[a4paper]{article}
\usepackage[ngerman]{babel}
\newcommand{\TT}{Test"=Text }
\begin{document}
This is a test whether the hyphen in \TT works or not.
In normal Test"=Text works.
\end{document}

In the text "= works fine, but as a command "= does not work. Any idea?

Answer 1

The babel-shorthand "= isn't activated yet when the macro is defined, so you have to activate it:

\documentclass[a4paper]{article}
\usepackage[ngerman]{babel}
\shorthandon{"}
\newcommand{\TT}{Test"=Text }
\shorthandoff{"}
\begin{document}
This is a test whether the hyphen in \TT works or not.
In normal Test"=Text works.
\end{document}

"Activated" means that it makes LaTeX think "Wait, there's something going on here, better check the next characters really carefully", just like a backslash \ tells it that a macro follows. \shorthandon{"} tells LaTeX to watch out for any ". (This only works for " afaik, it's babel specific.) Normally, " isn't activated until \begin{document}.

Answer 2

With babel v3.9, released in March 2013, you may also use the new KeepShorthandsActive option which "[t]ells babel not to deactivate shorthands after loading a language file, so that they are also availabe in the preamble" (manual, p. 11).

\documentclass[a4paper]{article}
% The following requires babel v3.9 (released March 2013)
\usepackage[ngerman,KeepShorthandsActive]{babel}
\newcommand{\TT}{Test"=Text }
\begin{document}
This is a test whether the hyphen in \TT works or not.
In normal Test"=Text works.
\end{document}